Hi,
Can I use 38 " radius for both mainlines if I space them out 2 1/2 inches
apart? I use modern era freight cars.
Thanks,
Chris
Yes and no. If they’re truly parallel lines and enter the arc at the same point, then its impossible. If you’re doing all sorts of other things, then yes.
If you’re doing all you say and using the same radius on the inside and outside track up to 90 degrees it will work fine. Start the inside curve before the outside curve and it will naturally open up un the middle of the curve and come back together at the end. At 38 inches it should work just fine, even with a Big Boy on the inside and passenger cars on the outside. Our corner modules usec 34 in radius to do the same thing.
To make this work you do need to have a longer tangent (straight) track on the outside curve than on the lead-in to the inside curve. Offhand, I don’t have the length of that tangent for a 38" radius, but we have used a similar trick on my modular club’s layout with 42" radius curves.
You cannot have two properly spaced, and parallel, tangent tracks leading to the ends of two nested curves of the same degree of curvature. Draw it out and see for yourselves.
I think the OP means 38" for the inner track and 40.5" for the outer track.
I doubt it - he specified 38" radius for both lines.
On that line, quick answer, No. The outside line would run into the inside line, or at least get way too close to it. I have a dual track main, and I use 36" for the inside and 38.5 for the outside. It’ll handle any length of car or loco quite easily.
Here is what I meant earlier:
Maybe steemtrayn intended to say that the OP would want to use 38" for the inner and 40.5" for the outer, or 38" for the outer and 35.5" for the inner.
Like gmcrail, I have found that the difference in radius between two relatively parallel tracks in HO scale is about 2.5". On my double mainline, the outer track radius is just over 32" and the inner track is just under 30".
Rich
I agree with Selector.
I have 36’‘, 32’’ and one end is 32’’ with a inner of true 28’'. I run a lot of 89 ft Intermodal flat cars and that works great… a dogbone, within, a dogbone…no reverse loops.
Take Care! [:D]
Frank
Yes! To prove it just take two pieces of curved track laid next to each other. Now this is just a single curve, as you get mutiple curves, it can get way more complex with long legs to do it, space we usualy don’t have!
If the inner curve is 38", the outer curve should be at least 40".
The more that I read this thread, the more I wonder what the OP had in mind when he asked the question.
Obviously, a circle of track will not fit inside another circle of track with the same radius.
So, what is the track configuration that the OP is contemplating for his double mainline?
Rich
If you truly mean to have two parallel tracks, then the spacing between track centerlines should be the same throughout the curve. So find the center of your curve and draw an arc at your desired radius. This describes the centerline of your inner track. Then find a point 2 to 2-1/2 inches farther out and draw another arc outside the first. This descries the centerline of your outer track. The ordinary rules of geometry say the outer arc will have a larger radius. If your two mainline tracks are not exactly parallel, then you can use whatever radius you want. Such an arrangement can be found on Cajon Pass, Sherman Hill, and many other prototype locations. Just make sure your two mains are never so close together that one train will sideswipe another.
Tom
When I built my layout I bought a Walther/Shinohara double crossover first and used their 2” center to center for my main lines, that become my dual track standard. When I hit my first curve I did the inside radius at 30” and the outside at 32½”. When I closed the curve I went back to 2”. That worked out for my Cab Forward freights and diesel powered passengers with 85” cars to pass without contact.
My only problem was at a dual track tunnel portal in a curve, a standard two track tunnel portal is too narrow for the overhang. I had to widen the portal casting ⅝” for an 85’ car on the inside track to clear and the Cab Forwards on the outside track. The inside radius on that curve is 34” with 36½” outside.
Mel
If you do a 90 degree curve its not so much an issue but your going to have your outer curve has to move further out. I don’t understand why you need to do this than just increasing your radius. A full 180 degree requires a lead in curve and out easement. Aside from that most curves really need easements but we don’t always do that do we…